From: joshua.goodall@...
Date: 2019-09-12T09:25:43+00:00
Subject: [ruby-core:94920] [Ruby master Feature#16102] `Symbol#call`

Issue #16102 has been updated by inopinatus (Joshua GOODALL).


I propose this general solution.

    diff --git a/array.c b/array.c
    index 3717c3ff34..3809af01cf 100644
    --- a/array.c
    +++ b/array.c
    @@ -6988,6 +6988,7 @@ Init_Array(void)
         rb_define_method(rb_cArray, "dig", rb_ary_dig, -1);
         rb_define_method(rb_cArray, "sum", rb_ary_sum, -1);
     
    +    rb_define_method(rb_cArray, "splat", rb_yield_splat, 0);
         rb_define_method(rb_cArray, "deconstruct", rb_ary_deconstruct, 0);
     
         id_random = rb_intern("random");

then:

    arrays = [["a", "b"], ["c"], ["d", "e"]]

    arrays.splat(&:product)
    #=> [["a", "c", "d"], ["a", "c", "e"], ["b", "c", "d"], ["b", "c", "e"]]


----------------------------------------
Feature #16102: `Symbol#call`
https://bugs.ruby-lang.org/issues/16102#change-81534

* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Since symbols have a `to_proc` method, it is natural to expect that they would appear in a method chain like:

```ruby
:some_symbol.to_proc.call(...)
```

In fact, I have use cases like this:

```ruby
arrays = [["a", "b"], ["c"], ["d", "e"]]
hashes = [{"a" => 1}, {"b" => 2, "c" => 3}, {"d" => 4, "e" => 5}]

:product.to_proc.(*arrays) # => [["a", "c", "d"], ["a", "c", "e"], ["b", "c", "d"], ["b", "c", "e"]]
:zip.to_proc.(*arrays) # => [["a", "c", "d"], ["b", nil, "e"]]
:union.to_proc.(*arrays) # => ["a", "b", "c", "d", "e"]
:merge.to_proc.(*hashes) # => {"a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5}
```

I request `Symbol#call` to be defined, which would implicitly call `to_proc` on the receiver and then the conventional `Proc#call` on the result. Then, I can do:

```ruby
:product.(*arrays) # => [["a", "c", "d"], ["a", "c", "e"], ["b", "c", "d"], ["b", "c", "e"]]
:zip.(*arrays) # => [["a", "c", "d"], ["b", nil, "e"]]
:union.(*arrays) # => ["a", "b", "c", "d", "e"]
:merge.(*hashes) # => {"a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5}
```

This would solve what proposals #6499, #6727, #7444, #8970, #11262 aim to do.

Notice that proposals #12115 and #15301 ask for `Symbol#call`, but they ask for different things (a method that returns a proc), and are irrelevant to the current proposal.



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